INTRODUCTORY ESSAY. 39 portance attached to locality, we helieve that botanists have no conception. Witness the fact, that several common Euro- pean garden-plants introduced into the grounds of the British Resident at Katmandu (Nipal), and thence re-imported to England, have been at once put forth in this country as new Himalayan discoveries, and specific characters invented for them. But instances of this multiplication of names are almost incredibly numinous: the corjmon English Yew has two Himalayan names; the Ptens aquilina ( English Bracken), seven; the eighteen known Indian species of Clematis are in Steudel's eNomenclator* ranked under forty names; and we may conclude by announcing our conviction, that more than one-half of the recorded species of Indian plants are spuri- ous, and that in many natural orders the undescribed species hardly equal in number those which require to be cancelled. The fact that almost every Himalayan plant has a vertical range of nearly 4000 feet, and many of 8000, is in itself a suggestive one. Several hundred species are dispersed from the Levant to the Indus, and many more from the Ganges to the Chinese Sea. Such instances of distribution in tropical plants are called strange and exceptional by unreflecting bo- tanists, who forget how many species are common to all longi- tudes between England and Kamtchatka, or to all the moun- tains of Europe; or to the Boeky Mountains of America, and those of Scotland and Norway; or to all latitudes between England and North Africa. The subject of geographical distribution leads to questions of practical importance, upon which we have a few remarks to offer, as eminently bearing upon all questions relating to the treatment of a systematic flora: these are,—1. Its depend- ence on the doctrine of specific centres. 2. The power of migration as capable of effecting the present distribution. 3. The general effects of migration in producing a much wider dispersion and ubiquitous diffusion of species than is generally admitted by botanists who have not investigated tropical floras, and especially continental ones.